AMBER Archive (2006)

Subject: RE: AMBER: ab initio terminology query

From: Yong Duan (
Date: Wed Nov 01 2006 - 17:17:43 CST

Dear Ilyas:

Indeed, you are correct. Cornell et al's calculation was done in gas-phase.
But Ross was also correct.

HF/6-31G* ESP has a special feature. It is higher than the one calculated at
higher level of theory. As a consequence, the charges are also larger. For
example, the dipole moments are about 10% larger than the "real" gas-phase
values calculated at higher level of thoery. In other words, if you want the
true gas-phase ESP, you need to use higher level theory, like the one Ross

Hope this clarifies.


> Cornell's paper (as fas as I understood) uses HF/6-31G* level
> of theory to
> get the ESP data points, and these calculations are done in
> gas-phase. If
> I am wrong, I will appreciate someone to correct me.
> Best,
> --
> Ilyas Yildirim

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